Deposition of AlN on Al substrates by reactive magnetron sputtering

Abstract

AlN has been a widely used material in electronics, optics and acoustics, and its outstanding mechanical properties indicate that it can also be an excellent candidate for tribological applications, especially on Al-based substrates which are soft and lack wear resistance. The present work explores the feasibility of depositing AlN films on 7076-T6 Al substrates by reactive magnetron sputtering. The effect of the working pressure and type of adhesion layer on the structure and performance (adhesion and hardness) of the films were investigated. Most of the resulting films developed a Thornton Zone 1 structure of poor intercolumnar cohesion and low density. The roughness of the AlN surface increased with working pressure. The development of certain textures as a function of working pressure did not affect properties significantly. The density, ductile nature of the substrate + adhesion layers and the thickness of the AlN films influenced the failure patterns that resulted from microhardness tests. Bonding of the AlN film to the adhesion layers was quite good; however, adhesion of this system to the Al substrate was fairly poor. This behavior was associated to an incomplete sputtering cleaning of the substrate prior to the deposition of the adhesion layer and it is the main area for future work.